Both colour and black and white photography are in widespread use for both still and moving pictures. In the television field at least, numerous techniques have been used for manipulating a television picture in various ways, e.g. by adding or inserting a second image into a window in a first image. However, the basic picture itself remains essentially unchanged.
There is also a known technique of "posterisation" which essentially reduces the image to individual areas of solid, uniform colour, rather than progressive changes in colour.
If one wants to achieve a hand drawn or painted appearance, then the principal current way of achieve this is to simply have a skilled artist draw or paint his perception of the subject in a chosen style, using conventional instruments such as pen, pencil and paintbrush.
The use of an artist is acceptable in some circumstances, and indeed it is almost certain that a human artist can always add some effect or detail that can never be achieved by a machine. Nonetheless, for many subjects, the use of an artist is either prohibitively expensive or unnecessarily time consuming. In particular, if one wishes to add such an effect to a television signal, then one has the problem of applying the effect to every frame of the signal, where there are thirty frames per second. Clearly, for even a very short sequence, the amount of work involved would be prohibitive.
Accordingly, it is desirable to provide a technique which enables a conventional colour or black and white image to be processed to achieve a variety of effects, principally giving an image a hand-drawn or painted appearance. Other more specialized effects can be provided, for example, an image can be rendered so that it appears to be a three-dimensional chrome surface. Ideally, one requires a method and apparatus that enables a variety of different techniques to be selected, manipulated and combined with one another to achieve an almost infinite variety of effects. It is further desirable-that such an effect should be capable of being applied relatively quickly and economically to a digitized television or motion picture signal, or a digitized still picture or photograph.